Incorporating recent advances in digital computer and numerical control techniques, analytical instruments are being designed to automatically interrogate a number of samples and measure two or more parameters during an interrogation. In typical measurement scenario, samples are positioned in locations on a carrier and the carrier is loaded into an instrument that automatically interrogates the locations. The gathered data may accurately be referred to as location-specific data since each of the interrogated samples is positioned in a known location on the sample carrier. Location-specific data may also be generated by an array of instruments, each of which is positioned in a known spatial relationship to the others.
Modern cytometers are representative of instruments that are designed to automatically analyze a number of samples on a carrier. These devices commonly interrogate particle-containing samples by illuminating the particles with one or more excitation light beams and detecting the colored light pulses that are generated by the particle-beam interaction. Flow cytometers focus the excitation light to define at least one excitation volume in a flow tube and the particles are transported through the focused light by a fluid flowing through the tube. Particles in a scanning cytometer are essentially stationary and the focused excitation light is scanned across the particles. In both classes of instrument, multicolored excitation beams may be formed by combining beams with different wavelengths. Information about the particles is provided by the wavelength, amplitude and shape of the colored light pulses.
Cytometers may be used to interrogate particle-containing biological samples containing molecules that are derived from living organisms. The particles in such samples may be surrounded by a solid, liquid or gaseous medium and often have fluorescent materials affixed to them to facilitate their interrogation. Commercial flow cytometers include capillary flow instruments such as the EasyCyte-Plus and PCA-96 manufactured by Guava Technologies of Hayward, Calif. and conventional sheath flow instruments such as the FACSCalibur manufactured by BD Biosciences of San Jose, Calif. The iColor Imaging Cytometer manufactured by Compucyte of Cambridge, Mass. is a representative scanning cytometer.
Advanced applications require cytometers with a large number of detectors as described in “Seventeen-colour Flow Cytometry: Unraveling the Immune System,” by S. P. Perfetto, et al., Nature Review Immunology, vol. 4, pp. 649-655 (2004) and “Beyond Six Colors, a New Era in Flow Cytometry,” S. C. DeRosa, et al., Nature Medicine, vol. 9, pp. 112-117 (2003). U.S. Pat. No. 6,683,357 issued to Clifford A. Oostman et al. on Jan. 27, 2004 describes a representative multiple laser cytometer system with a reflective filter system for advanced applications. Embodiments of the Oostman patent may have three or more excitation volumes and more than a dozen detectors.
Due to its complexity, the data generated by the interrogation of one of more samples with a cytometer are typically analyzed using a digital computer. Commercial software packages for cytometry data analysis include FCS Express from DeNovo Software, Los Angeles, Calif., FlowJO from the Stanford Shared FCS facility and licensed through Stanford University, Stanford, Calif. and CellQuest PRO from BD Biosciences, San Jose, Calif. Techniques for cytometry data analysis are also disclosed in U.S. Pat. No. 6,178,382 issued to Mario Roederer, et. al. on Jan. 23, 2001 and “Interpreting flow cytometry data: a guide for the perplexed,” L. Herzenberg et al, Nature Immunology, Volume 7, pp. 681-685, July 2006.